Tweety bird meets super sweety. Super tweetie that is. But why the meet? If our hearing gives out at maximally 22kHz when we’re young—and likely is down to 15kHz by the time we sink untold coin into our hifis—why bother with add-on tweeters? Isn’t one enough? And whilst we’re at it, how about the upper limit of Redbook? With CD or equivalent files, there’s nothing recorded any higher. So even if certain instruments can eclipse our hearing threshold like muted trumpet, it’s just measurement kit which tells that tale. And bona fide high-resolution files. But not our ears.
All that’s common sense. And as usual for hifi, there’s more to it. The most obvious and not debatable of that is power response. This relates to how a speaker energizes the room. Because direct-radiating loudspeakers suffer progressively narrowing dispersion with rising frequencies—the flood light of the bass registers eventually becomes a spot light in the treble—there’s less reflective boundary reinforcement for the higher bands.
The easiest way to check this is to move off-axis. The farther you go, the more the upper treble rolls off. That’s because you move outside its narrow spot light. Now try to listen from behind the speakers. Unless they’re omnis or di/bipoles, the sound will dull by lacking upper harmonics. Dynamically too it’s debatable whether a 1-inch soft-dome tweeter is really up to the task of maintaining linear dynamic contrast against the far beefier artillery that’s used for the lower bands.
Here common sense intrudes again. First off, who listens from behind the speakers? Check. All serious listeners know that for best stereophonic results, you want to be in the sweet spot. Check. As far as acoustic live music goes, it’s nearly always darker and more treble muted than glossy bright modern hifi playback. If it’s amplified music, it’s usually far more bass-heavy as well. With that it’s hard to argue. But not impossible. Let’s try then.
With live music, eye sight supplements our hearing to confirm positioning, distance and certain music events when we both see and hear a drummer’s sticks or a pianist’s hands. With playback, all visual confirmation is gone. Now it’s solely up to our ear/brain to recreate a three-dimensional illusion of a sound field peopled with performers. And it turns out that clean intelligible treble data are vital in this pursuit of audible space and greater imaging specificity.
These ‘extra-visual’ audio effects do not occur with live music. They needn’t either since there we have the use of our eyes. But these effects are achievable with a well-sorted system particularly if one addresses the typical losses in HF power response due to limited dispersion and insufficient radiating surface.
Owners of Duevel or German Physiks omnis already know how their type can enlarge the sweet spot to such an extent that it hardly matters where one sits. Anthony Gallo’s patented CDT tweeter with its 180° dispersion is famous for its soundstaging and imaging. It also supplies far greater diaphragm area to be more dynamic.
If one desires to turn listening into a more social than solitary pursuit, a wider sweet spot is mandatory. Don’t be a selfish pig, spread the joy around. If your hifi doubles for video, a broad sweet spot is essential to anchor voices to the screen for those outside the center seat. My German Physiks HRS-120 completely eliminate the need or desire for a center channel. Obviously this applies to music playback too. You can move about and multi-task without sacrificing sound quality. Hogging ‘the’ seat becomes a meaningless exercise and throwback to the Dark Ages of the lone-wolf audiophile in the basement.
A wide or everywhere sweet spot is the perfect antidote when you entertain guests.
To combine omnipolar spaciousness and airiness with the more surgical imaging precision of direct-radiators means simply combining the two. That’s why EnigmAcoustics for example have a traditional if slightly large dome tweeter on their Mythology M1 monitor and a planar monopole ESL super tweeter. But that yet doesn’t go the full hog.
For the whole pork we need to look at Elac and their two flagship models. Those combine an AMT-type ‘folded ribbon’ tweeter with a circular true 5µm aluminium ribbon super tweeter on top. Where this gets interesting for today’s discussion is that this omni tweet is available separately as the add-on 4pi Plus.2. At €2098/pr, it is unapologetically serious money. With adjustable sensitivity from 84-92dB; a variable hi-pass at 10/12/15K with ultra-precision switches; a cast enclosure with cast wave guides; and terrific performance… it also delivers on its coin.
With a 2nd-order filter and 3’500-53’000Hz bandwidth, this super tweeter covers the same ground as modern ceramic, beryllium, diamond or ribbon tweeters do. Where it completely goes beyond all of them is with its 4pi radiation. And it is that which restores full-space high-frequency in-room coverage for a more linear power response.
If you plant this mushroom-shaped glossy black device atop your conventional box speaker (a flat top is a must), you graft to a typical direct radiator an omnipolar mid to high treble. In the critical presence region, the main tweeter remains dominant. That locks in directivity and image precision. Above 7kHz where its power response drops, the Elac kicks in to restore full spaciousness, air and sparkle.
This is decidedly not a function of additional bandwidth which we’d not hear in the first place (though there is research to suggest that our skin and skull bones are receptors for frequencies beyond where our ears give out). This is a function of radiation pattern.
So far so good. Even unbelievers should have followed thus far to concede these facts whilst likely and fairly questioning what ultimate merit or necessity they represent. Where it gets weird not just for them is that the obvious operational band of the mid/high treble of a super tweeter can and routinely does have audible effects far lower. Here the how and why dissolve into mystical mists.
Anyone who has experimented with quality infrasonic subwoofers set up properly knows how even basic vocals with sparse guitar accompaniment will sound richer, more present and embedded in more audible space when the sub is active. Common sense—which sometimes is just that, common not special—points at all lack of apparent recorded LF for such music to dispute the effect. Those who’ve tried it know better though even if they can’t properly explain how and why. Once you apply subwoofers for the 20-40Hz octave to larger ensembles and more complex music, the advantages in scale and power are undeniable. Even tone colors can feel more saturated as though blacks were deeper.
With quality super tweeters, subjective time keeping aka beat fidelity can improve. A lot of rhythm work occurs in the upper bass. Why that would get better when a super tweeter at best might contribute slightly more audible upper harmonics to those instruments is, admittedly, strange. But with a super tweeter of Elac’s concept and execution (or Enigma’s particularly with their own monitor), it is unmistakable. Besides more air and space, there’s also more snap and spunk.
Just as vital as it is with subwoofers, proper super tweeter adjustment facilities are a must to create a proper blend. Too little and you won’t hear anything; too much and you’ll get needly, pixilated and dry. Though Elac’s 4pi Plus.2 does very deliberately ‘play the room’, this action doesn’t trigger or ride any room modes of the sort which exaggerate certain bass frequencies to get boomy and muddy up the higher bands.
If music subwoofers are rare critters barely accepted by the card-carrying career audiophile, super tweeters are even rarer and still more outré. Without personal experience, it’s also very hard to come up with a compelling ‘scientific’ argument to rationalize them. Arguments to dispute them however are easy pickings. To even want to try one of these devices will require real curiosity and a certain amount of mental independence that doesn’t rely on peer approval and easy answers.
To conclude, music in Western Electric’s days was happy with 50Hz to 15kHz bandwidth. If you hear a quality vintage system properly set up, you’ll likely concur that nothing essential is missing. Once you cue up some modern synth-bass endowed fare with snarling electric bass on top, that opinion could change of course. But it’s important to not paint the addition of the fully developed first and last octaves as essential. That would be deceptive. The meat of the music does occupy a far narrower middle. Today’s KIH is about spicing up that meat.
That makes the pursuit of the infrasonic subwoofer augmented on the other end with an omni super tweeter a rather more final connoisseur’s thing. It’s an advanced enhancement which, in many ways, can be ‘better’ than real life. As such, it’s not ‘realistic’ by definition even if it feels more real. Thankfully hifi is about an illusion. That illusion takes place between and not in our ears. Hence we’re free to design and tweak that illusion until it most pleases us. Here I propose that those with otherwise licked and polished systems might consider a carefree fling with a super tweetie. Who knows… it could turn into a long-term super sweetie affair.